1. Field of the Invention
The present invention relates generally to threat detectors, and more particularly to multi-modal particle detectors for detecting chemical, biological, and explosives threats.
2. Background Art
The detection of chemical, biological, and explosives threats is becoming increasingly difficult due to the continuously changing nature of such threats. For example, new combinations of chemicals are used for explosives, new delivery mechanisms are used with lethal chemical and biological compounds, and new constructions are employed for improvised explosives devices (IED). Detection is also made difficult due to threats arising in environments or locations that are not conducive for deploying traditional threat detection mechanisms.
Many threat detection devices are described in the art. For example, the background section of U.S. Pat. No. 6,610,977 ('977 patent), which is incorporated herein by reference in its entirety, includes an extensive description of various threats and threat detection mechanisms. Generally, threat detection mechanisms may be classified into trace and bulk detection. In trace detection, minute quantities of materials are detected either in vapor or particulate form. The related trace detection mechanisms include electron capture, gas chromatography, mass spectroscopy, ion mobility spectrometry, Raman spectroscopy, plasma chromatography, biological markers and laser photo acoustics. Trace detection mechanisms are primarily suited for detection of threat substances in the environment. Bulk detection mechanisms are primarily used to detect bulk quantities of threat substances that are concealed and carried in various forms, including baggage. They include x-ray, gamma-ray, neutron activation and nuclear magnetic resonance.
Despite the large number and variety of threat detectors that are commercially available, there is a paucity of multi-modal detectors that are capable of detecting multiple threats based on different properties of threat particles. To be effective, multi-modal detectors must detect threat particles efficiently and with reduced false alarm rates for a variety of threat particles, while also being capable of flexible deployment in various environments. Some attempts at developing multi-modal detectors have been made. For example, the '977 patent discloses a combination of multiple known detectors in a predetermined decision hierarchy. U.S. Pat. No. 5,668,342 ('342 patent) discloses a method of detecting multiple types of explosives materials by illuminating that material with multiple energy sources. The '977 patent combines different sensors as they are without an effort to increase the efficiency available by integration of selected techniques, and without an effort to increase the ability to deploy. The '342 patent only addresses the detection and neutralization of explosives in baggage check applications.
What is needed therefore, is a multi-modal particle detector that is capable of efficiently detecting multiple types of threats including chemical, biological, and explosives threats with reduced false alarm rates, and is capable of being deployed reliably in a number of different environments.